1. Field of the Invention
The present invention relates to a quality of service (QoS) of data communication, and more particularly, to a method and apparatus for securing a quality of service (QoS) of data communication by controlling a handover of a multi-mode-multi-band terminal, which can be used in a variety of wireless communication networks, between heterogeneous/homogeneous communication networks using an exchange of packets between a data reception side and a data transmission side.
2. Related Art
Existing wireless communication networks, such as code division multiple access (CDMA), wideband CDMA (WCDMA), Wibro (which is based on the same IEEE 802.16 standard as WiMax, but is designed to maintain connectivity on the go, tracking a mobile terminal at speeds of up to 37 miles per hour), high-speed downlink packet access (HSDPA), etc., typically include a distribution system which serves as a backbone wired communication network, such as Ethernet that supports servers and one or more access routers (ARs) or communication switch systems to link with other networks, including, for example, the Internet, and one or more control modules, known as wireless access points (APs) or base stations arranged at designated locations in the wireless communication networks, each supporting wireless communication with a number of mobile terminals, which can be mobile devices such as laptops, PDAs, cellular phones, or other wireless communication devices, within its designated service area (transmission range) and providing access to the distribution system. The wireless access point (AP) or base station is provided to access network resources, via the distribution system, while the mobile terminals are provided to communicate with the wireless access point (AP) or base station, via wireless links, as specified by standard communication protocols.
As the number of mobile communication users has increased rapidly, and mobile communication services supporting multimedia have become more sophisticated in a variety of types and standards, these mobile communication services are required to provide mobile communication users with a seamless service. As a result, it is important to perform a handover between heterogeneous/homogeneous communication networks.
FIG. 1A is a diagram of a conventional handover between example homogenous wireless communication networks. Referring to FIG. 1A, the distribution system is a wired communication network 110. If the wireless communication networks are wireless local area networks (LANs), standard communication protocols for a wireless LAN, such as IEEE 802.11 standards are utilized. An access router 120 and one or more access points (APs), for example, a first access point (AP1) 130 and a second access point (AP2) 140 are also utilized to perform a handover when a mobile terminal is moving between service areas covered by the first access point (AP1) 130 and the second access point (AP2). In such a wireless LAN provided by the IEEE 802.11 standard, an access router (AR) 120 at a transmission side accesses the wired communication network 110, and transmits data to a mobile terminal, via an access point (AP) 130 or 140. In this regard, it is assumed that the mobile terminal moves from a service area provided by a first access point (AP1) 130 to a service area provided by a second access point (AP2) 140. The mobile terminal compares a signal strength of the first access point (AP1) 130 with a signal strength of the second access point (AP2) 140. If the signal strength of the second access point (AP2) 140 is higher than the signal strength of the first access point (AP1) 130, the mobile terminal transmits a signal requesting a handover from the first access point (AP1) 130 to the second access point (AP2) 140, via the access router (AR) 120. The access router (AR) 120 then sends a signal to perform the handover from the first access point (AP1) 130 to the second access point (AP2) 140 to the mobile terminal so that the mobile terminal transmits data through the second access point (AP2) 140.
If the wireless communication networks are homogeneous CDMA and WCDMA networks, the handover between example homogeneous CDMA and WCDMA networks is performed the same way as in the wireless LAN networks. However, the access router 120 may be replaced by a mobile communication switch station 120, and the access points (APs) 130 and 140 may be replaced by base stations 130 and 140.
FIG. 1B is a diagram of a conventional handover between example heterogeneous wireless communication networks. Referring to FIG. 1B, the distribution system can include both a CDMA switch system 150 and a WCDMA switch system 170. The handover is performed between a CDMA network and a WCDMA network. A mobile terminal may be a multi-mode, multi-band mobile phone which can operate in both the CDMA and WCDMA networks and can communicate, when moving from a CDMA base station 160 to a WCDMA base station 180. The mobile terminal also compares a signal strength of the CDMA base station 160 with a signal strength of the WCDMA base station 180. If the signal strength of the WCDMA base station 180 is higher than the signal strength of the CDMA base station 160, the mobile terminal transmits a signal requesting the handover to a CDMA switch system 150. The CDMA switch system 150 transmits a signal for preparing the handover to a WCDMA switch system 170. When the handover is completely prepared, the WCDMA exchange system 160 informs the CDMA exchange system 150 of the fact so that the multi-mode multi-band terminal may transmit the data through the WCDMA base station 180.
As shown in FIGS. 1A and 1B, a handover is performed, via communication between a mobile terminal at a reception side and an access router (AR) or a switch system at a transmission side. In particular, since the handover is performed regardless of a transmission side, the transmission side that transmits data is not informed of a particular wireless communication network in which the mobile terminal at the reception side performs the handover. Therefore, a problem occurs if the transmission side transmits data to a particular wireless communication network to which the mobile terminal at the reception side belongs before the handover is performed.
For example, the mobile terminal at the reception side performs a handover from a wireless LAN, as shown, for example, in FIG. 1A, having a maximum data transmission rate of 2 Mbps to a WCDMA network, as shown, for example, in FIG. 1B having a maximum data transmission rate of 384 Kbps. Therefore, if the transmission side used to transmit data at a data transmission rate of 1 Mbps in the wireless LAN, as shown in FIG. 1A, having the maximum data transmission rate of 2 Mbps, is not informed of another wireless network, for example, a WCDMA network, to which the mobile terminal at the reception side moves to, and still transmits data at the data transmission rate of 1 Mbps after the handover is performed, the mobile terminal at the reception side cannot receive the entire data transmitted by the transmission side. If the transmission side transmits music or video image data for real-time streaming, the reception side cannot seamlessly listen to music or view the motion video image in real-time.
Accordingly, there is a need for a new and efficient mechanism to ensure quality of services (QoS) as a mobile terminal moves from one wireless communication network to another wireless communication network.